The Effect of Strain Rate on the Breakage Behaviour of Rock
Date
2008
Authors
Jackson, K.
Kingman, S.
Whittles, D.
Lowndes, I.
Reddish, D.
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Archives of Mining Sciences // Polish Academy of Sciences. Committee of Mining, 2008; 53(1):3-22
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K. Jackson, S.W. Kingman, D.N. Whittles, I.S. Lowndes, D.J. Reddish
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Abstract
For the optimum design of a rock crushing plant the breakage characteristics of the rock under the loading conditions imposed by the crusher are required. Often the determined static mechanical values fail to characterise the energy required and degree of fragmentation of the material within the crusher. This paper describes a laboratory and numerical investigation into the affect of strain rate on the energy requirements and breakage characteristics of three different sedimentary rocks. For each rock type high speed uniaxial compression tests were carried out at six different strain rates over the range 2.57 × 10–5 strain/s to 0.02 strain/s. Changes in the stress-strain behaviour were discovered indicating the importance of strain rate on breakage characteristics. For each of the rock types the stress/strain curves showed an increase in ductility as the strain rate increased and it was calculated that the energy used in bringing the specimen to fracture increased by up to 50%. The increase in energy was also accompanied by an increase in the degree of fragmentation achieved. The numerical modelling of the high speed compression test was undertaken for the sandstone using the discrete element method code PFC3D produced by Itasca. The numerical modelling reproduced the increase in energy requirements for fracture and an increase in the degree of fragmentation. The modelling also predicted that this trend would continue at strain rates of 1 strain/s that would be anticipated in rock crushers.
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